The 69-year-old leader of the National Union of Ethical Citizens was returning from a political rally late Saturday with his bodyguard when the chopper encountered bad weather, said the reports, citing Paraguay's airport authorities.

All the three on board, including a pilot, were killed in the crash, they said.

In April, Oviedo stood for the presidential election as Paraguay's third-largest opposition party.

The retired general and former army chief was accused of plotting to overthrow governments in the 1990s and served half of a 10-year sentence before being released.